COT 2004 - mercury in fish and shellfish

The UK Committee on Toxicity updated its fish and shellfish mercury advice after the 2003 JECFA methylmercury PTWI revision. The statement reviews FSA survey data for imported/farmed fish and shellfish, UK dietary exposure estimates, and blood mercury data. It treats fish mercury as methylmercury-relevant exposure context but repeatedly notes that some intake estimates use total mercury measurements that do not distinguish inorganic and organic forms.

Key numbers

• JECFA methylmercury PTWI: reduced from 3.3 µg/kg bw/week to 1.6 µg/kg bw/week in June 2003.
• 1998 MAFF survey context: mercury levels in tested fish and shellfish were low, and the highest-level consumer estimate was 1.1 µg/kg bw/week including mercury intake from the rest of the diet.
• 2002 FSA fish survey: all but 3 species had mean mercury levels within 0.01 -0.6 mg/kg of fish.
• Highest-mean species: shark 1.52 mg/kg, swordfish 1.36 mg/kg, and marlin 1.09 mg/kg.
• Fresh tuna: mercury ranged from 0.141 to 1.50 mg/kg, with mean 0.40 mg/kg; one of 20 samples exceeded 1 mg/kg, and the maximum in the other 19 samples was 0.62 mg/kg.
• Canned tuna: mean mercury level was 0.19 mg/kg.
• UK adult blood mercury: mean 1.6 µg mercury/L; 97.5th percentile 5.88 µg mercury/L; the highest blood mercury level corresponded to approximately 5.39 µg/kg bw/week (0.77µg/kg bw/day) if at steady state.
• Table 6.1 canned-tuna exposure: adults mean 0.30 µg/kg bw/week, 97.5th percentile 1.05; adult women mean 0.34, 97.5th percentile 1.19; toddlers mean 0.84, 97.5th percentile 2.45.
• Table 6.1 whole-diet total mercury exposure: adults mean 0.31 µg/kg bw/week, 97.5th percentile 1.19; toddlers mean 0.56, 97.5th percentile 2.17.
• Table 6.2 one weekly portion for adults: shark 3.04, swordfish 2.68, marlin 2.20, fresh tuna 0.80, and canned tuna 0.38 µg/kg bw/week.
• Table 6.2 one weekly portion for ages 1.5-4.5 years: shark 5.24, swordfish 4.62, marlin 3.79, fresh tuna 1.38, and canned tuna 0.66 µg/kg bw/week.
• The statement notes that one weekly 140 g portion of shark, swordfish, or marlin would result in methylmercury exposure close to or above 3.3 µg/kg bw/week in all age groups.

Methods (brief)

The statement synthesizes the 2002 FSA survey of mercury in imported fish/shellfish and UK farmed fish, the 1998 MAFF marine fish and shellfish survey, national fish-consumption data, and blood mercury data from British adults. Dietary exposure calculations use total mercury occurrence data for specific fish and shellfish categories and note that fish mercury is predominantly methylmercury, while whole-diet total mercury exposure also includes inorganic mercury.

Implications

Certification (HMTc): This is A-tier UK seafood mercury context for fresh tuna, canned tuna, shark, swordfish, marlin, salmon, prawns, and whole-diet exposure. It should not be treated as a direct MeHg concentration table unless the source explicitly frames the calculation as methylmercury exposure.

Courses: The statement is useful for teaching the difference between total mercury concentration, methylmercury-relevant fish exposure, and whole-diet mercury intake that can include inorganic mercury.

App: The source can support UK seafood advice context and fish species notes for mercury, especially predatory fish and tuna.

Wiki pages this source may touch

• seafood
• fresh-fish
• canned-fish
• shellfish
• fish-marine-predatory
• mercury-total
• mercury-methyl

Verification notes

• PDF text was extracted with pdftotext -layout to /tmp/hmi_row_1454.txt; paragraphs 6.25-6.59 and Tables 6.1-6.2 were re-read before writing.
• Identity checks before creation: title phrase, raw handle MFK_cot-2004-mercury-fish, raw SHA-256 67363b5429bbc693ad3eccb84b4cb1874ffe5d691e97b8630332fbe1e114f44d, and cite key cot2004-mercury-fish-shellfish were searched in wiki/sources/; no existing source page was found.
• Units are preserved as mg/kg, µg/kg bw/week, µg/kg bw/day, and µg mercury/L.
• Speciation: occurrence concentrations are reported as mercury/total mercury. The page does not promote every total-mercury value to MeHg; it records the source’s methylmercury exposure framing separately.
• Closed vocabulary: exact fish-species ingredient slugs exist for shark, swordfish, and marlin; other named matrices such as salmon and prawns remain descriptive or route through broad fish/shellfish slugs.

Page history

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